once in poly

Example with a knob. First once in poly is OFF,(a polyphony of 6 creates 6 inlets) then option once in poly is ON and creates only 1 inlet.

The actual data type of a once in poly node is similar to an array. Once inspected you can see that it is an array the length of the nb of polyphony selected for that specific sub-patch.
Although an array in data-type, once in poly disguises it's data representation and only addresses the first index by masking as a single-data node.